| Author | Message | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1932 Registered: 1-2001 |
No trouble -- glad you got it working. This is one of those problematic high current circuits that can frazzle the connectors and/or PCBs (BTDT) -- I guess we should be thankful a CPU isn't involved!  | ||
| Robert Taylor (4rebob)
New member Username: 4rebob Post Number: 18 Registered: 9-2002 |
Steve, I've got heat again !!!!! It was #1, no power to the system. One of the big "apm" connectors to the fuze board was loose. After reading your post, I got out the wiring diagram and found the main power feed to the fan motor, it was dead. And yes, the system appears to be very similar to the TR. I always forget rule #1 of Mondial troubleshooting "check the fuse block". Thanks for your help Bob | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1925 Registered: 1-2001 |
Bob -- I'm really just guessing that your Mondial fan blower control arrangement is similar to the TR (and 328 IIRC) so you really need to get the proper schematic and have a look. If you had the "full-on works, anything else doesn't" problem then I'd be willing to bet a few $ your Mondial does have the same architecture and the power transistor was futzed (or the switch electronics was bad) -- but I could still be wrong since I've not seen your Mondial schematic. Here's what I know TR-wise: 1. With the engine running and an AC button pushed, one side of the fan blower motor should go +12V -- if not, you've got something bad in the upstream +12V - fuseboard - fuse - relay - fuseboard network. 2. At anything less than full-speed, the motor current flows thru the power transitor -- i.e., the fan speed switch electronics controls the (small) current flowing into the base and out the emitter to ground. This base-to-emitter current in turn controls the large current flowing in the (permanent) branch from +12V (when present) -to- motor -to- collector -to- emitter -to- ground. 3. At full speed, the fan speed switch electronics puts a ground signal on a different wire to close a -113 relay, which in turn, puts ground directly on the side of the motor hooked to the collector so it becomes +12V -to- motor -to- ground and the motor runs full speed (and no/little transistor current involvement). If the +12V is present at the motor per above and if you connect/jump the collector to ground the motor should run full speed -- IF YOUR MONDIAL IS LIKE A TR -- IT MIGHT NOT BE! Since you're reporting all dead, I'd first be checking if the +12V is present at the motor. Alternatively (if you can't get to the motor connections), if you turn things "on" and the collector doesn't go +12V you've got problem #1 (On the TR, the collector terminal is the case of the transistor) -- IF YOUR MONDIAL IS LIKE A TR -- IT MIGHT NOT BE! HTH and Good Luck... | ||
| Robert Taylor (4rebob)
New member Username: 4rebob Post Number: 17 Registered: 9-2002 |
Steve, I think I had "full on only" a couple of times before I got "no more blow at any speed". If I cross connect 2 of the wires going to the transistor, can I go back to "full on"? I'd like to make sure it's the transistor and not the motor or something else. | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1923 Registered: 1-2001 |
Bob -- The power transistor bracket for my TR was also pop-riveted in place so to replace it I had to drill out the old rivets and use new rivets. If you put the fan speed knob to the max "on" position (ignition key "on" and the STOP button is not pushed) will the fan run at full speed (even though the slower speeds don't work)? | ||
| Robert Taylor (4rebob)
New member Username: 4rebob Post Number: 16 Registered: 9-2002 |
My 83 Mondial�s heater / AC fan won�t turn on anymore. The heater / AC gets hot / cold, but the fan won�t blow. According to the workshop manual (and the way I think it used to work); The push buttons (Stop, AC, AE, defrost) control the vacuum actuated �flaps� that control the air flow direction and power to the system. Power to the system is either off (Stop) or on (any of the other three push buttons). Am I correct so far? The output air temperature is controlled by the temperature knob combined with an interior temperature sensor, several other sensors, and a �brain� module. This temperature control system controls the hot water flow and AC pump to regulate the hot / cold that goes to the heater box and comes out of the vents. Am I wrong yet? The fan operates independently of the temperature control system. If the system power is on (the Stop button is not pushed), the fan should work. The speed of the fan is controlled by the fan switch, from off to fully on. You should be able to keep air moving around all the time. Everything works, but the fan won�t turn on. If this is the way it is suppose to work? Does anyone know it the temperature control system has anything to do with the fan? I�d hate to have to try and figure it out. I�ve got things torn apart. The fan switch has a bunch of wires going to it and appears to be much more complicated that I though it would be. It has an internal fuze that looks good to me. From what I�ve read, the likely suspect might be the �power transistor� located inside the heater box (reached through the main dash air vent). Anyone have any ideas on how to test this? How does it come out? It appears to be on a bracket that is riveted in. Drill the rivets? Any way to bypass it and make the fan come on? Any one have any ideas on what else to check? Once again, an elegant overly complicated system to accomplish a simple task. Thanks Bob |